Gantry cranes are typically used to handle cargo in ports, where they are exposed to various weather conditions such as rain. Driving of the gantry cranes requires great precision, for example when picking up and stacking cargo containers. Accidents in cargo handling using gantry cranes can have serious consequences to the equipment and personnel involved in the accident. In the case an accident takes place, the cargo handling operation using the gantry crane is stopped. The single accident may have consequences also to cargo handling of other cranes, for example by blocking another crane from moving over a stack of containers. Thereby accidents can reduce operational efficiency of the cranes and even the whole port.
Laser scanners are used in gantry cranes for aiding in driving the cranes and cargo. Laser scanners transmit laser beams through a surface permeable to laser light, and receive reflected laser beams back through the surface. The transmitted and reflected lasers are used to measure distances to objects. In order to facilitate correct operation of the laser scanner, the permeable surface that the laser beams travel through should be clean from dirt and water. However, depending on the weather conditions, e.g. rain, humidity, fast temperature changes, water in the form of rain drops or fog, can be formed on the surface. On the other hand particles such as pollen may accumulate to the surface over time. However, the pollen and water cause attenuation, refraction and scattering of the laser beams that travel through the surface, which cause inaccuracy to the operation of the laser scanners. In small amounts, the inaccuracies may slow down the cargo handling by the gantry cranes, but in high amounts the inaccuracies may cause accidents that endanger the equipment and nearby personnel. Cleaning the water and dirt from the laser scanners may be dangerous and time consuming, due to the locations of the laser scanners being difficult to access e.g. due to the elevation of the location from the ground. Due to personnel safety requirements, cleaning of the laser scanners necessitates stopping of the crane, which leads to stopping also other crane(s) working on the same stack of containers. This reduces the operational efficiency of the cargo handling.